I've found a bunch that look a lot like this but not from 1958 or 1959. Also find a lot of quarters black like this and believe it's probably some kind of PMD or dirty/rusted. From what I understand a true sintered planchet Nickel error should still have some shine/luster to it in addition to the grayish coloring. Guess a real one could get dulled or worn over time as well so not sure but since it looks so similar to the others I've come across not uniform across the entire surface I'd say PMD. My cousin found one were still not quite sure of but is in great condition and seems to fit, he posted it on here a while back ...

Yes it seems getting it authenticated it the only way to know for sure with something like this. Understandably there are no accurate numbers as to the amount of them produced and it seems in the late 50's the Mint must have gotten lazy and stopped changing the cleaning solution making bunches of these. The one on the right in your photo looks identical to the one my cousin has.

To make things more difficult and annoying there seems to be several ways to make similar looking coins manually. Looks like there are a bunch of ways to electroplate them in different solutions and read some people for whatever reason do something called "bluing" which I had never heard of and seems is mainly used guns to coat and protect the underlying metal a black/gray look.

In general I'd say until officially authenticated it could be anything. I they can go for a few hundred dollars more or less depending on the condition but doubt anyone would buy one not slabbed/certified anyway....unless it for real cheap.

Well, sounds like it's worth a shot getting one authenticated and if it comes back genuine, send in the other. Although my pics don't show it, they both have good luster and steps visible.(Took these pics in a hurry this morning just to post).As always, thanks for teaching me...it amazes me what you can learn on the internet....I think it's gonna be popular

Update on the nickels I posted above. I sent one to ANACS and requested a variety attribution of sintered planchet.I recieved an email notifying me that it was graded as MS63, but no mention of the variety or problems. Does that seem possible ? I should recieve the actual coins shortly but it sure has me puzzled.

ANACS has done that to me also in the past. They email and give the grade but no variety and you don't know until it comes back. It will be interesting to see if they have the variety on the case. Let us know.